The object of this invention is a method for feeding blanks of the type presented in the preamble to claim 1. The object of this invention is also a device for feeding blanks of the kind presented in the preamble to claim 8.
It is known to use liquid packaging paperboard for the manufacture of cylindrical containers having an upright cylindrical body formed by joining the opposed vertical edges of a blank provided with a heat-sealable coating and having end closure members secured to the upper and lower open ends of the body, the upper end closure member having a hole covered with, for example, an openable closure cap or closure strip. Containers of this type are used for the sterile and airtight packaging of different beverages.
The container into which the packaged substance, such as a drink, is fed at a latter stage, is manufactured automatically in a package forming unit consisting of a series of so-called mandrels around which the body part is formed by wrapping. The mandrels are arranged in a rotating structure, which transfers the mandrels from one processing station to another. At these stations, specific operations are carried out one at a time, thus resulting step by step in a can-like casing which, at the last processing station, is disengaged from the mandrel and transferred to the filling unit for filling and closing.
The apparatuses discussed above are known to a person skilled in the art and they are described, for example, in European patents EP-B1-0 038 488 and EP-B1-0 018 470. It is especially characteristic of the methods presented in these patents to wrap the blank around the mandrel by using a mechanical pressing member which presses one edge of the blank against the side surface of the mandrel and moves with the mandrel""s rotation, which pulls the blank around the mandrel to form a closed structure, after which the sides are sealed,
U.S. Pat. No. 4,318,703 also discloses a method in which sidewall blanks are fed in succession onto a wheel consisting of radially projecting mandrels. One after another, the blanks are transferred from a stockpile on a conveyor in a horizontal position through a heating station, where hot air is blown from opposite sides onto the edges of the blanks, after which they are fed one at a time onto a mandrel which has rotated to the feeding position, and are then wrapped around the mandrel. U.S. Pat. No. 4,490,130 discloses a rotation wheel that transfers the blanks in succession through the side edge heating unit prior to the wrapping stage. The publication EP-B1-0 456 011 discloses a similar principle of blank pre-heating, in which rectangular-shaped sheets are cut from a continuous blank strip, and after the cutting unit, the blank sheets advance in succession on a conveyor in a horizontal position through an edge heating unit before the blanks are wrapped about the mandrels.
Feeding separate blanks into the forming unit requires accurate timing and accurate positioning of the blanks at the mandrels before wrapping. In a rotating structure it is typical that the mandrels come to the wrapping unit at intervals of less than one second, for example 0.5 seconds, which requires reliable functioning of the actuators and of their control, since when the mandrel rotates to the wrapping unit, the blank must be ready in the right position with respect to the mandrel.
This invention relates to a method that can simplify the feeding of the blank to the wrapping unit and ensure that the blanks are brought at the speed required by the rotation speed of the mandrels to the right position at the wrapping unit. What is mainly characteristic of the method in order to achieve this is described in the characterising part of the claim 1. The blanks are brought in the form of a continuous web to the wrapping station, where they are detached, for example by cutting, and transferred onto the wrapping mandrel. A continuous blank web is more easily controlled, and its transfer can be arranged in a downward direction, which saves space in the horizontal direction. The edge of the blank web is advanced to the proximity of the wrapping mandrel perpendicularly to the mandrel""s axial direction in such a way that it is aligned, at least partly, with the mandrel, after which a blank of a specific length is detached from the web, the blank being then immediately ready to be pushed into contact with the side surface of the mandrel by one direct movement at a right or a slightly oblique angle to the blank""s longitudinal direction. The detachment point on the web is at a distance determined by the length of the blank and at this point a detachment means operates, which has been programmed to cut the web along a line across its longitudinal direction. The detachment means is most preferably a cutting means, which cuts the web by a stroke directed towards at its surface.
As to the other advantageous embodiments of the invention, reference is made to the accompanying dependent patent claims and to the description that follows.